diff --git a/enterprise/app/models/concerns/agentable.rb b/enterprise/app/models/concerns/agentable.rb
index c12e15f52..810cf2556 100644
--- a/enterprise/app/models/concerns/agentable.rb
+++ b/enterprise/app/models/concerns/agentable.rb
@@ -24,7 +24,8 @@ module Concerns::Agentable
         current_time: format_current_time(state[:timezone]),
         conversation: state[:conversation] || {},
         contact: config['feature_contact_attributes'].present? ? state[:contact] : nil,
-        campaign: state[:campaign] || {}
+        campaign: state[:campaign] || {},
+        message_length_limit: state[:message_length_limit]
       )
     end
 
diff --git a/enterprise/app/services/captain/assistant/agent_runner_service.rb b/enterprise/app/services/captain/assistant/agent_runner_service.rb
index 197b2e39b..059b11fc1 100644
--- a/enterprise/app/services/captain/assistant/agent_runner_service.rb
+++ b/enterprise/app/services/captain/assistant/agent_runner_service.rb
@@ -20,6 +20,9 @@ class Captain::Assistant::AgentRunnerService
   def generate_response(message_history: [])
     message_to_process, context = run_payload(message_history)
     @last_run_result = runner.run(message_to_process, context: context, max_turns: 10)
+    @last_run_result = rewrite_oversized_response(@last_run_result) if response_too_long?(@last_run_result)
+
+    raise "Captain response exceeds the channel limit of #{message_length_limit} characters" if response_too_long?(@last_run_result)
 
     process_agent_result(@last_run_result)
   rescue StandardError => e
@@ -93,6 +96,28 @@ class Captain::Assistant::AgentRunnerService
     response
   end
 
+  def rewrite_oversized_response(result)
+    runner.run(
+      "Your previous response was #{response_text(result).length} characters, but this channel allows a maximum of " \
+      "#{message_length_limit} characters. Rewrite it within the limit while preserving the essential information. " \
+      'Do not call tools or perform new actions.',
+      context: result.context,
+      max_turns: 10
+    )
+  end
+
+  def response_too_long?(result)
+    message_length_limit && response_text(result).length > message_length_limit
+  end
+
+  def response_text(result)
+    extract_text_from_content(result.output).to_s
+  end
+
+  def message_length_limit
+    @message_length_limit ||= Captain::MessageLengthLimit.for(@conversation&.inbox)
+  end
+
   def error_response(error_message)
     {
       'response' => 'conversation_handoff',
diff --git a/enterprise/app/services/captain/assistant/runner_state_helper.rb b/enterprise/app/services/captain/assistant/runner_state_helper.rb
index d2d6146f8..3b43e5ecc 100644
--- a/enterprise/app/services/captain/assistant/runner_state_helper.rb
+++ b/enterprise/app/services/captain/assistant/runner_state_helper.rb
@@ -31,6 +31,7 @@ module Captain::Assistant::RunnerStateHelper
   def build_conversation_state(state)
     state[:conversation] = slice_attrs(@conversation, CONVERSATION_STATE_ATTRIBUTES)
     state[:channel_type] = @conversation.inbox&.channel_type
+    state[:message_length_limit] = Captain::MessageLengthLimit.for(@conversation.inbox)
     state[:contact] = slice_attrs(@conversation.contact, CONTACT_STATE_ATTRIBUTES) if @conversation.contact
     state[:campaign] = slice_attrs(@conversation.campaign, CAMPAIGN_STATE_ATTRIBUTES) if @conversation.campaign
     state[:contact_inbox] = slice_attrs(@conversation.contact_inbox, CONTACT_INBOX_STATE_ATTRIBUTES) if @conversation.contact_inbox
diff --git a/enterprise/lib/captain/message_length_limit.rb b/enterprise/lib/captain/message_length_limit.rb
new file mode 100644
index 000000000..0d5918269
--- /dev/null
+++ b/enterprise/lib/captain/message_length_limit.rb
@@ -0,0 +1,23 @@
+class Captain::MessageLengthLimit
+  DEFAULT = 10_000
+  CHANNEL_LIMITS = {
+    'Channel::FacebookPage' => 2_000,
+    'Channel::Instagram' => 1_000,
+    'Channel::Line' => 2_000,
+    'Channel::Sms' => 320,
+    'Channel::Telegram' => 4_096,
+    'Channel::Tiktok' => 6_000,
+    'Channel::Whatsapp' => 4_096
+  }.freeze
+  TWILIO_LIMITS = {
+    'sms' => 320,
+    'whatsapp' => 1_600
+  }.freeze
+
+  def self.for(inbox)
+    return unless inbox
+    return TWILIO_LIMITS.fetch(inbox.channel.medium) if inbox.twilio?
+
+    CHANNEL_LIMITS.fetch(inbox.channel_type, DEFAULT)
+  end
+end
diff --git a/enterprise/lib/captain/prompts/assistant.liquid b/enterprise/lib/captain/prompts/assistant.liquid
index a8f1dada3..722ca0631 100644
--- a/enterprise/lib/captain/prompts/assistant.liquid
+++ b/enterprise/lib/captain/prompts/assistant.liquid
@@ -50,6 +50,11 @@ Always respect these boundaries:
 
 When a Response Guideline or Guardrail explicitly requires transfer for a matched condition, follow it instead of the generic consent-first handoff defaults below.
 
+{% if message_length_limit -%}
+# Channel Requirements
+Keep your response at or under {{ message_length_limit }} characters so it can be delivered through this channel.
+{% endif -%}
+
 # Decision Framework
 
 ## 1. Analyze the Request
diff --git a/enterprise/lib/captain/prompts/scenario.liquid b/enterprise/lib/captain/prompts/scenario.liquid
index afa2cd420..667c009dc 100644
--- a/enterprise/lib/captain/prompts/scenario.liquid
+++ b/enterprise/lib/captain/prompts/scenario.liquid
@@ -47,6 +47,11 @@ Always respect these boundaries:
 {% endfor %}
 {% endif -%}
 
+{% if message_length_limit -%}
+# Channel Requirements
+Keep your response at or under {{ message_length_limit }} characters so it can be delivered through this channel.
+{% endif -%}
+
 {% if tools.size > 0 -%}
 # Available Tools
 You have access to these tools: